1. Field of the Invention
This invention relates to the remote control of the inflation or deflation of a volume from a gaseous fluid under pressure, and more particularly the remote control of the inflation pressure of an automotive vehicle tire on a wheel.
2. Description of the Prior Art
In the above field of application, it is known it is sometimes useful to be able to control the inflation pressure of tires remotely, in order to match the tire traction with the conditions of the terrain over which the vehicle is moving. This is in particular the case for cross country vehicles that must advance under the most favorable conditions, whether ground surface is hard, stony or even soft, without the driver having to stop the vehicle to adapt the inflation pressure of the different tires manually.
This application is of course only given as an example, because in many other fields it is also found useful and even necessary to be able to adapt the inflation pressure of any volume, and to do so at a distance.
To solve the above problem, the prior art offers only a few solutions. One known system employs a valve which, when in its normal rest position, closes a path of circulation between the volume and an available source of fluid pressure.
Whenever it is desired to inflate the volume, the valve is driven against the action of a recall spring, in such a way as to open the circulation circuit.
Whenever it is desired to partially deflate the volume, a fluid under pressure is applied to raise the valve and the source of pressurized fluid is isolated, to keep the valve open during the time needed to produce a slow decompression, through an expansion valve, of the fluid initially confined in the volume.
Such a installation requires a particularly complicated remote control circuit, which becomes even more complex when one or more volumes have to be controlled from a distance, as is the case in the application to automotive vehicles.
Beyond this disadvantage, it should be noted that the deflation phase calls for a major transit time, which is established by means of a complex system, remote-controlled by an expensive and fragile logic control circuit.
In the particular application to the technical field at hand, the prior art proposes no satisfactory system, considering that each volume, consisting of a vehicle wheel, must necessarily be isolated from the control system by a rotary joint which is held at pressure throughout the entire inflation phase.
Such a rotary joint is thus intensely stressed in rotation and in pressure, so that the friction packing(s) providing the rotary seal are subject to major stresses and are unable to provide reliable service.
This disadvantage is of particular concern with vehicles which receive hard use.
These systems provide simultaneous and relatively slow deflation of the tires, which is also a disadvantage.
A remotely controlled pneumatic valve is also known which is made of two bodies, an inflation and deflation body, delimiting two cavities, called the inlet and escape cavities, communicating with each other through an opening which forms two seats, one in each chamber, for two piloted valves. This communicating line, between the seats, consists of a channel leading through a connection opening into the inflated volume, the inlet chamber being in communication with a connection opening into a control system, while the escape chamber communicates with the ambient atmosphere through vent holes.
Such a valve is satisfactory, but may be considered expensive to construct. Furthermore, it size, does not lend itself well to an integrated installation in a vehicle wheel.